The Nellcor N-180 has three oximetry operating modes. The N-180 performs an automatic self-test and calibration upon power on. This unit has both visible and audible oximetry displays with alarms for SpO2 and pulse rate. The audible alarms are configurable or the user can preset limits for adults or neonates. The Nellcor N-180 has a built-in battery back up. DRE sells this model refurbished.